Fixture for making glass-to-metal seals or the like and methods of making the same

ABSTRACT

A HIGH TEMPERATURE CERAMIC FIXTURE IS DISCLOSED FOR EMPLOYMENT IN HOLDING METAL AND GLASS COMPONENTS IN PROPER POSITION FOR FUSING OF GLASS-TO-METAL SEALS THEREBETWEEN. THE LIFE OF THE FIXTURE AND THE QUALITY OF THE GLASS-TO-METAL SEALS ARE IMPROVED BY A UNIQUE METHOD OF DEPOSITING A UNIFORMILY ADHERENT COATING OF CARBON ON THE FIXTURE AT RELATIVELY LOW TEMPERATURES. THE CARBONCOATED CERAMIC FIXTURE IS MORE DURABLE AND ITS COATING CAN BE PERIODICALLY REPLENISHED DURING USAGE WITHOUT THE NECESSITY OF REFIRING OR REPLACING THE FIXTURES.

March 2, 1971 A. T. JOHNSON 3,567,490

FIXTURE FOR MAKING GLASSTO'METAL SEALS OR THE LIKE AND METHODS OF MAKING THE SAME Filed Oct. 4, 1967 Fig.l.

. "Neuron v Arthur T. Jdhnsbn I z zagw United States Patent 3,567,490 FIXTURE FOR MAKING GLASS-TO-METAL SEALS OR THE LIKE AND METHODS OF MAKING THE SAME Arthur T. Johnson, Providence, R.I., assignor to GTI Corporation Filed 0d. 4, 1967, Ser. No. 672,919 Int. Cl. B44d 1/14 US. Cl. 117-54 11 Claims ABSTRACT OF THE DISCLOSURE A high temperature ceramic fixture is disclosed for employment in holding metal and glass components in proper position for fusing of glass-to-metal seals therebetween. The life of the fixture and the quality of the glass-to-metal seals are improved by a unique method of depositing a uniformly adherent coating of carbon on the fixture at relatively low temperatures. The carboncoated ceramic fixture is more durable and its coating can be periodically replenished during usage without the necessity of refiring or replacing the fixtures.

The present invention relates to an improved fixture for holding metal and glass components or the like in proper position during fusing to produce metal-to-glass seals therebetween, and more particularly to a ceramic fixture, having a protective coating wherein the coating is longer lived and is replenishable and to methods of making the same.

In the past, a number of such fixtures have been proposed. In one instance the fixture has been fabricated from solid carbon or graphite. Although such fixtures are useful in some applications, at elevated temperatures they tend to crack and require frequent replacement. The solid carbon or graphite fixtures moreover are fragile and difiicult to handle in use.

Similar fixtures fabricated entirely from ceramic materials also have been utilized. These fixtures suffer from the disadvantages that the fused glass or the like tends to adhere thereto.

Attempts have been made to remedy this disadvantage of ceramic fixtures by depositing a coating of carbon on the ceramic fixtures. In general, a more satisfactory ceramic fixture has been produced. The carbon coating, however, according to previous applicative methods has been deposited as a relatively thin coating and has been baked on the ceramic fixtures at elevated temperatures in special atmospheres to prevent oxidation of the coating. In practice, it has been found that the life of prior carboncoated ceramic fixtures has been relatively short and that the quality of the fused components has been impaired. The application of coating to prior carbon-coated fixtures requires special equipment and the coating cannot be replenished by users of the fixtures.

Usage of previously proposed fixtures for the indicated purposes has also resulted in excessive numbers of rejects among the fused components as a result of breakage or leakage.

I overcome these disadvantages of the prior art by providing a ceramic fixture having a protective coating thereon which exhibits an extended life under customary conditions of usage of more than ten times that of known ceramic fixtures. The character of the protective coating which my invention enables one to apply to ceramic fixtures improves considerably the quality of the finished fused components or devices. My invention permits the Patented Mar. 2, 1971 production of fused devices with a smaller number of rejects resulting from breakage or of imperfect seals.

Briefly, my invention provides improved coated ceramic fixtures for the purposes described and also improved methods for coating the fixtures, for example with a carbonaceous material. Thus, one form of my novel method involves a proper cleaning and preparation of the surface of the ceramic fixtures, coating the ceramic fixture with a graphic suspension or the like, baking the coated fixtures at a relatively low temperature, and spraying the baked fixtures with a graphitic suspension or the like. My novel method not only produces more durable ceramic fixtures, but also the carbon coating thereof can be applied in a simpler manner. The use of high temperature furnaces and special firing atmospheres is avoided. Moreover, the life of the coating applied to the fixture in accordance with my invention can be prolonged by periodie application of protective coating material throughout the useful life of the fixtures.

I accomplish these desirable results by providing a coated ceramic fixture for holding components in proper position during fusing of said components to join said components, said fixture comprising a ceramic base member, a first protective coating uniformly adhered to the surface of said base member, and a second protective coating uniformly covering said first coating to prolong the life of said first coating and to protect the surfaces of said components when engaged by the fixture.

I also desirably provide a coated ceramic fixture wherein each of said coatings contain a carbonaceous material.

I also desirably provide a method for coating a ceramic fixture, said method comprising the steps of immersing said fixture in a suspension of carbonaceous material, removing said fixture from said suspension, baking said fixture to adhere said material to said fixture, and applying a protective second coating of carbonaceous material to said adhered coating.

I also desirably provide a method for coating a ceramic fixture wherein said fixture is immersed in an aqueous solution of sulphuric acid and acetic acid prior to immersion in said carbonaceous suspension.

I also desirably provide a method for coating a ceramic fixture wherein said fixture is placed in boiling water having a wetting agent dissolved therein prior to immersion in said aqueous solution.

I also desirably provide a method for coating a ceramic fixture wherein the second application of carbonaceous material is accomplished by spraying after cooling said fixture and the sprayed fixture is permitted to dry at room temperature.

I also desirably provide a method for coating a ceramic fixture wherein the second coating of said fixture is replenished periodically during use of said fixture.

During the foregoing discussion, various objects, features and advantages of the invention have been set forth. These and other objects, features and advantages of the invention together with structural details thereof will be elaborated upon during the forthcoming description of certain presently preferred embodiments of the invention and presently preferred methods of practicing the same.

In the accompanying drawings I have shown certain presently preferred embodiments of the invention and have illustrated certain presently preferred methods of practicing the same, wherein:

FIG. 1 is a longitudinally sectioned view of a typical ceramic fixture coated in accordance with my invention, and

FIG. 2 is an enlarged sectional view of a portion of the fixture shown in FIG. 1.

Referring now more particularly to the drawings the exemplary form of my invention shown therein includes a coated fixture 10, which is useful in supporting, for example, metal and glass components 12 and 14 during the fusing process to form a glass-to-metal seal 16 therebetween. Thus, the fixture includes recess 18 shaped generally to receive the glass component 14 and recess 20 shaped to receive likewise the metal component 12.

The fixture 10 as better shown in FIG. 2 is provided with a first baked-on layer 22 of carbon, graphite or other protective material and a second, sprayed-on layer 24 of similar material. The layer 22 provides a suitable base surface to which the sprayed-on coating 24 can properly adhere. On the other hand the second layer 24 protects and extends the life of the baked-on uniformly adherent coating layer 22, and the two coating layers 22, 24 together provide a proper surface of engagement with juxtaposed portions of the metal and glass components 12, 14.

It has been found that the use of my dual-coating ceramic fixture 10, including the coating layers 22, 24, produces a superior glass-to-metal seal16 and does not mar the adjacent surfaces of the metal and glass components 12, 14 in contrast to previously proposed fixtures. I have also found during usage of the fixtures such as the fixture 10 that the outer carbonaceous layer 24 can be periodically renewed without the use of firing or baking or special gaseous environments or the like. I have found, on the contrary, that I can periodically replenish the outer coating 24 on the fixture 10 as by spraying or dipping or the like to renew the outer coating layer 24 followed by drying the newly applied layer 24 for a brief interval at room temperature and without a special atmosphere. Thus the outer coating 24 can be replenished periodically by the user and without the use of special equipment.

Desirably, I apply the coatings 22, 24 to the fixture 1G or an analogous ceramic fixture by placing the fixture in boiling water for about 30 minutes. Preferably a wetting agent including about 10 volume percent of Triton X-100 or equivalent is added to the water. Triton X100 is a trademark for an organic poly-ether alcohol available from Rohm and Haas Co.

Following this step I remove the boiled fixture, preferably without drying, to a second cleaning solution including desirably about 35- volume percent sulphuric acid (H 80 15 volume percent acetic acid (CH OOOH) and 50 volume percent water (H O). The last-mentioned cleaning solution preferably is maintained at a temperature of about 150 to 160 F and the fixture is permitted to remain therein for about 15 minutes.

Following this interval, I desirably remove the fixture from the last-mentioned solution and immerse and rinse the fixture thoroughly in distilled Water.

Again without drying, I remove the fixture from the distilled water rinse and immerse the fixture immediately in a graphitic suspension or a suspension of other suitable carbonaceous material. Desirably the fixture is permitted to remain in the suspension for about 30 minutes, with the temperature of the suspension being maintained about 120 F. Preferably, I formulate the graphitic suspension in the following proportions: 25 grams of concentrated graphite (Aquadag) in 100 cc. of water. Aquadag is a trade name for a finely divided colloidal dispersion of graphite available from Acheson Colloids Co.

I then remove the fixture from the graphitic suspension and, again desirably without drying, place the fixture in a baking oven for a period of 3-4 hours. Desirably the temperature of the oven is maintained about 250 F. for this period. No special atmosphere is required, and therefore, I employ an air atmosphere. The baking step of my method together with the preliminary surface preparational steps produces a uniformly adherent coating on the fixture of the metal from the graphitic suspension. This well adhered initial coating protects the surfaces of the fixture and more importantly those surfaces of the metal and glass components 12, 14, which are engaged by the fix- 4 ture 10. Most importantly the adhered coating provides a proper base to receive the second or outer carbonaceous coating applied in the final step of my method. This latter protective coating otherwise would not adhere to the bare ceramic surface of the fixture 10.

After removing the fixture from the oven and after permitting the fixture to cool to a temperature of about F. (room temperature), I desirably spray the fixture with Aquadag spray graphite. Following this operation the fix= ture is permitted to dry for a period of about 30 minutes at room temperature and in an ordinary or air atmosphere. The fixture is then ready for use. The second carbonaceous layer can also be applied by brushing or dipping a graphitic suspension on the coated fixture or by analogous methods.

In any event it will be seen that the second protective Coating 24 thus applied to the fixture 10 can be periodically renewed without the use of special equipment or without the necessity of returning the fixtures to the manufacturer for reprocessing. Discarding of used fixtures is therefore frequently avoided.

During usage of the fixture, the outer coating layer of the fixture desirably is replenished periodically. This is accomplished by reapplying the outer coating layer 24 as by spraying and drying in the manner described above.

. Where the fixture is employed for the fusing of glass and metal components to effect a glass-to-metal seal therebetween, the fixture desirably is recoated as by spraying after every two passes through the furnace employed for fusing the glass and metal parts.

From the foregoing it will be apparent that novel and efiicient forms of fixtures for making glass-to-metal seals have been described herein. While I have shown and described certain presently preferred embodiments of the invention and have illustrated presently preferred methods for practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodiment and practiced Within the scope of the following claims.

What is claimed is:

1. A coated ceramic fixture for holding components in proper position during fusing of said components to join said components, said fixture comprising a ceramic base member, a first baked on graphite coating uniformly adhered to the surface of said base member, and a second low temperature dried graphite coating uniformly covering said first coating to prolong the life of said first coating and to protect the surfaces of said components when engaged by the fixture.

2. A method for coating a ceramic fixture, said method comprising the steps of immersing said fixture in a suspension of graphitic material for a time and at a temperature sufficient to form a coating of graphitic material thereon, removing said fixture from said suspension, heating said fixture to a temperature sufficient to form a baked on graphitic coating adhering to said fixture, and applying a protective second coating of graphitic material to said adhered coating and drying the same thereon at low tem perature so that the moisture removed.

3. The method according to claim 2 wherein said fixture is immersed first in an aqueous solution of sulphuric acid and acetic acid and then in distilled water prior to immersion in said graphitic suspension.

4. The method according to claim 3 wherein said fixture is placed in boiling water having a polyether alcohol wetting agent dissolved therein prior to immersion in said aqueous solution of acids.

5. The method according to claim 2 wherein said fixture is baked at a temperature of about 250 F. for an interval of about 34 hours.

6. The method according to claim 5 wherein said fixture is baked in an air atmosphere.

7. The method according to claim 2 wherein the second application of graphite material is accomplished by spraying after cooling said fixture and the sprayed fixture is permitted to dry at room temperature.

8. The method according to claim 7 wherein said sprayed fixture is permitted to dry for an interval of about 30 minutes in an air atmosphere.

9. The method according to claim 3 wherein said fixture is immersed in said aqueous solution for an interval of about 15 minutes and at a temperature of about 150 F. to 160 F.

10. The method according to claim 4 wherein said fixture is boiled for an interval of about 30 minutes and said wetting agent is a polyether alcohol.

11. The method according to claim 2 wherein the second coating of said fixture is replenished as it wears during use of said fixture.

References Cited UNITED STATES PATENTS ALFRED L. LEAVITT, Primary Examiner 10 W. F. CYRON, Assistant Examiner US Cl. X.R. 

